1. Field of the Invention
The present invention relates to a printing apparatus, such as an ink jet printer and an ink jet plotter, and also to an ink cartridge detachably attached to a printer main body of the printing apparatus. More specifically the invention pertains to a technique of processing and storing required pieces of information in the ink cartridge.
2. Description of the Related Art
The printing apparatus like the ink jet printer and the ink jet plotter mainly includes an ink cartridge, in which one or plural inks are kept, and a printer main body with a print head to carry out actual printing operations on a printing medium. The print head ejects ink fed from the ink cartridge onto the printing medium, such as printing paper, so as to implement printing on the printing medium. The ink cartridge is designed to be detachably attached to the printer main body. A new ink cartridge has a predetermined quantity of ink kept therein. When the ink kept in an ink cartridge runs out, the ink cartridge is replaced with a new one. Such a printing apparatus is arranged to cause the printer main body to calculate the remaining quantity of ink in the ink cartridge based on the amount of ink transferred from the print head and to inform the user of a state of running out of the ink, in order to prevent the printing procedure from being interrupted by the out-of-ink.
The data on the remaining quantities of inks are generally stored only in the printer main body or in a printer driver that controls the printer. In the event that a first ink cartridge is replaced with a second ink cartridge in the course of the printing operation, the information relating to the first ink cartridge, such as the data on the remaining quantities of inks, are thus lost or made wrong.
One proposed technique to solve this problem utilizes a non-volatile memory provided in the ink cartridge and causes the required data, for example, the data on the remaining quantities of inks, to be written from the printer main body into the non-volatile memory (for example, JAPANESE PATENT LAID-OPEN GAZETTE No. 62-184856). In the case of replacement of the ink cartridge during the printing operation, this technique ensures the storage of the data on the remaining quantities of inks.
The data on the remaining quantities of inks is required to have a relatively high accuracy, in order to inform the user of the precise timing of replacement of the ink cartridge. Storage of such data with a high accuracy in the ink cartridge makes the required storage capacity undesirably large. In the case where the data on the remaining quantities of inks has only a low accuracy, on the other hand, the timing of an alarm of the ink end state, in which a certain ink in the ink cartridge is running out, may significantly be contradictory to the actual remaining quantity of ink. In a structure that updates the data on the remaining quantities of inks at a power-off time, the printer main body reads the data on the remaining quantity of each ink from the ink cartridge at every start of power supply and interprets the read-out data as a value of the lower limit within the preset accuracy. By way of example, it is assumed that the data stored in the ink cartridge expresses the remaining quantity of each ink as a value of percentage in the range of 0 to 100% and has a length of 1 byte (8 bits) and an accuracy of 1%. When the data read from the ink cartridge is ‘50’, the printer main body can not specify the exact value of the data. The data ‘50’ may be obtained by rounding 50.9 or 50.1. In order to prepare for the worst, the printer main body deals with the data ‘50’ as a value of the lower limit ‘50.0’.
In this structure, even in the case where only a little quantity of ink is used, data should be reduced by 1%. This means that repeating such use 100 times causes the data on the remaining quantity of ink in the ink cartridge to be equal to 0, although there is still a sufficient quantity of ink remaining in the ink cartridge. In another structure that does not reduce data by 1% in the case of use of a little quantity of ink, repeating such use many times causes an alarm of the ink end state not to be given even if the actual remaining quantity of ink is equal to zero. In an ink cartridge with a memory or a printer using such an ink cartridge, the storage capacity of several bytes for each ink is required to monitor the remaining quantity of ink precisely. In the case of a color ink cartridge that keeps a plurality of different color inks in a casing thereof, a certain storage capacity should be allocated to each color ink. For example, in the case of a color ink cartridge including five color inks, if the required storage capacity for each color ink is 4 bytes, the total storage capacity is as large as 5×4=20 bytes (20×8=160 bits).
Increasing the data length to be written makes it difficult to write all the required data within a short time period after a power-off operation. When a power switch mounted on a switch panel of the printer is operated, the applicable sequence enables the printer to confirm conclusion of the writing operation of data into the memory of the ink cartridge, before actually turning the power source off. In the case where the power supply is forcibly cut off on the side of the power line by pulling the power plug out of the socket or turning off the power of an extension connected to a computer, however, the writing operation of data into the memory of the ink cartridge should be completed within a very short time period. If the power voltage is lost in the course of the writing operation, the reliability of data in the ink cartridge is significantly lowered. This prevents the ink cartridge from being used adequately. The use of the memory having a large storage capacity undesirably increases the manufacturing cost of expendable ink cartridges. This is also undesirable from the viewpoint of resource saving.
The problems discussed above arise in any printing apparatus that does not directly measure the remaining quantity of ink or the amount of ink consumption in an ink cartridge but causes the printer to compute such data, and in an ink cartridge attached thereto. Such printing apparatus includes an ink jet-type printing apparatus that uses ink obtained by mixing or dissolving a pigment or a dye with or in a solvent and ejects ink droplets in the liquid state to implement printing, a printing apparatus that uses an ink cartridge with an ink toner accommodated therein, and a thermal transfer-type printing apparatus.